A dual-clutch transmission combines certain features of manual and automatic transmissions. In a dual-clutch transmission, a first input clutch is applied to engage any odd gear sets of a gearbox, while a second input clutch is applied to engage the even gear sets. An onboard transmission control module predicts the next gear to be selected using available control inputs such as engine acceleration and braking levels, and then commands engagement of the next gear ahead of the impending shift. Use of a dual-clutch transmission can improve the speed of a gear shift relative to those occurring in a conventional automatic transmission, typically with improved shift control and increased power.
A dual-clutch transmission may be either wet or dry. The gearbox and both input clutches of a wet dual-clutch transmission are cooled and lubricated by fluid that is circulated via an engine-driven pump and/or an auxiliary fluid pump. In a dry dual-clutch transmission or dDCT, the gearbox remains lubricated while the two input clutches remain dry. As a result, a dDCT tends to experience greater performance variation relative to a wet DCT design. Such performance variation is due largely to the wider variation in both the bulk temperature as well as the surface temperature of the non-lubricated input clutches.